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preface to fifteenth edition

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10.16 SECTION 10<br />

The resin has the ability <strong>to</strong> be oriented by a drawing process and crystallized <strong>to</strong> yield a highstrength<br />

product.<br />

10.3.15.3 Unsaturated Polyesters. Unsaturated polyesters are produced by reaction between two<br />

types of dibasic acids, one of which is unsaturated, and an alcohol <strong>to</strong> produce an ester. Double bonds<br />

in the body of the unsaturated dibasic acid are obtained by using maleic anhydride or fumaric acid.<br />

10.3.15.4 PCTA Copolyester. Poly(1,4-cyclohexanedimethylene terephthalic acid) (PCTA) copolyester<br />

is a polymer of cyclohexanedimethanol and terephthalic acid, with another acid substituted<br />

for a portion of the terephthalic acid otherwise required. It has the following formula:<br />

10.3.15.5 Polyimides. Polyimides have the following formula:<br />

They are used as high-temperature structural adhesives since they become rubbery rather than<br />

melt at about 300C.<br />

10.3.16 Poly(methylpentene)<br />

Poly(methylpentene) is obtained by a Ziegler-type catalytic polymerization of 4-methyl-1-pentene.<br />

Its key properties are its excellent transparency, rigidity, and chemical resistance, plus its resistance<br />

<strong>to</strong> impact and <strong>to</strong> high temperatures. It withstands repeated au<strong>to</strong>claving, even at 150C.<br />

10.3.17 Polyolefins<br />

10.3.17.1 Polyethylene. Polymerization of ethylene results in an essentially straight-chain highmolecular-weight<br />

hydrocarbon.<br />

CH 2 "CH 2 : [9CH 2 9CH 2 9] n<br />

Branching occurs <strong>to</strong> some extent and can be controlled. Minimum branching results in a “highdensity”<br />

polyethylene because of its closely packed molecular chains. More branching gives a less<br />

compact solid known as “low-density” polyethylene.

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